Oyo Rooms — Wrongly charged extra at check in

I booked one room for one night 23-24 June 2021 in OYO 77436 mahalaxmi park hotel, Chennai for my father. He was wrongly charged with additional Rs200 in the name of sanitisation charges. Since I had paid the entire booking amount beforehand online I could not cancel the booking. I have complained the same on the app but no response as the hotel manager is denying that he charged extra. The booking id concerning is HFDC2563.
The same hotel charged extra for me the next day also quoting same charges but I got the same back by complaining on the app . But the booking HFDC2563 extra amount has not been refunded yet. Oyo has denied the refund stating that the hotel manager did not charge anything extra, kindly tell that how a hotel will charge extra on one day and won't charge extra the other day?? The hotel is charging extra from all the customers. Kindly look into the matter and get me my refund.